Effect of Hydroxyurea on Mortality and Morbidity in Adult Sickle Cell Anemia: Risks and Benefits Up to 9 Years of Treatment

Context: Hydroxyurea increases levels of fetal hemoglobin (HbF) and decreases morbidity from vaso-occlusive complications in patients with sickle cell anemia (SCA). High HbF levels reduce morbidity and mortality. Objective: To determine whether hydroxyurea attenuates mortality in patients with SCA. Design: Long-term observational follow-up study of mortality in patients with SCA who originally participated in the randomized, double-blind, placebo-controlled Multicenter Study of Hydroxyurea in Sickle Cell Anemia (MSH), conducted in 1992-1995, to determine if hydroxyurea reduces vaso-occlusive events. In the MSH Patients' Follow-up, conducted in 1996-2001, patients could continue, stop, or start hydroxyurea. Data were collected during the trial and in the follow-up period. Setting: Inpatients and outpatients in 21 sickle cell referral centers in the United States and Canada. Patients: Two-hundred ninety-nine adult patients with frequent painful episodes enrolled in the follow-up. Follow-up data through May 2001 were complete for 233 patients. Intervention: In the MSH, patients were randomly assigned to receive hydroxyurea (n=152) or placebo (n=147). Main Outcome Measures: Mortality, HbF levels, painful episodes, acute chest syndrome, and blood cell counts, The randomized trial was not designed to detect specified differences in mortality. Results: Seventy-five of the original 299 patients died, 28% from pulmonary disease. Patients with reticulocyte counts less than 250000/mm³ and hemoglobin levels lower than 9 g/dL had increased mortality (P=.002). Cumulative mortality at 9 years was 28% when HbF levels were lower than 0.5 g/ dL after the trial was completed compared with 15% when HbF levels were 0.5 g/ dL or higher (P=.03). Individuals who had acute chest syndrome during the trial had 32% mortality compared with 18% of individuals without acute chest syndrome (P=.02). Patients with 3 or more painful episodes per year during the trial had 27% mortality compared with 17% of patients with less frequent episodes (P=.06). Taking hydroxyurea was associated with a 40% reduction in mortality (P=.04) in this observational follow-up with self-selected treatment. There were 3 cases of cancer, 1 fatal. Conclusions: Adult patients taking hydroxyurea for frequent painful sickle cell episodes appear to have reduced mortality after 9 of years follow-up. Survival was related to HbF levels and frequency of vaso-occlusive events. Whether indications for hydroxyurea treatment should be expanded is unknown.